In the technology of automation and process control, field devices are often used for determining a process variable in a process flow. Field devices for determining flow rate, fill level, differential pressure, temperature, etc. are generally known. They serve for registering the corresponding process variables: mass or volume flow rate, fill level, pressure, temperature, etc. The field devices produce signals, which act as measures for the registered process variables. As a rule, the field devices are, in part, or in total, connected with a control room or control system. The measurement signals are forwarded to the control room or control system. Normally, the entire process control is done at the control room or control system, where the various measurement signals of the different field devices are evaluated and, on the basis of the evaluation, control signals are produced for other field devices (actuators), e.g. valves, which then control the course of the process.
Signal transfer between the field device and the control room, or control system, occurs e.g. over current loops or a data bus, using known standards (Profibus, Foundation Fieldbus, CAN-Bus). The field devices are part of a production installation, whose management is very complex. Information concerning the production installation, or the components, or the field devices, begins to accumulate starting with the first day of planning. This information concerns essentially design, layout, procurement, installing, startup, operation and maintenance, i.e. the whole life cycle.
Maintenance is an essential cost factor of a production installation. For maintenance, various pieces of information are needed, which partly are in the purview of the user and partly in that of the manufacturer. Thus, only the user knows which of its applications are critical and what the loss of a field device would mean for production. For field devices being used in critical applications, greater attention to maintenance is always justified. In turn, only the manufacturer knows when production will end for which field devices in the foreseeable future. If the user alone drafts a maintenance plan, such is going to be incomplete, since essential information held by the manufacturer is not available.
If the manufacturer produces a maintenance plan for a production installation, it will, as a rule, lack the necessary information about the field devices in use, and, even if it has this information, it will still probably not know how critical the individual field devices are for the uninterrupted flow of production.